A. Field of the Invention
The present invention relates to a detector for detecting a back corona condition in an electrostatic precipitator and setting back the current.
B. Background Art
It is known in the art to detect voltage breakdowns on the high voltage side of electrostatic precipitators. In such precipitators, the d.c. voltage applied directly to the electrodes is slowly and gradually increased or ramped up to but not exceeding a voltage level at which a breakdown in the precipitator gap occurs. However, voltage breakdown may occur when a voltage, arising from another portion of the precipitator circuit, is providing a current of large magnitude to the precipitator. This additional applied voltage must be quickly detected and reduced to prevent loss of precipitator efficiency. In essence, voltage breakdown is detected and voltages that create large current flows through the plates of the precipitator are reduced in value.
A similar problem occurs when a layer of dust builds up on the electrodes of the precipitator such that a back corona condition occurs in which the current being supplied to the precipitator plates becomes consumed in the back corona instead of being used to precipitate the suspended gas particles. More current will then be fed to the precipitator, but the increase in current will be used to sustain the back corona rather than for providing particle precipitation. Therefore, a detector has been needed that would sense the point at which current no longer increased in direct proportion to the voltage thereby terminating efficient particulate precipitation. An object of the invention is to reduce current until a point has been reached where the current no longer increases faster than the voltage such that the precipitator would be operated at this point. By reducing the current sufficiently, the back corona condition would be minimized so that more of the current flowing to the precipitator would be used for precipitating particulate matter rather than to feed the back corona condition.